1. Field of the Invention
The present invention relates to a type of microsurgical instrument used in treatment of intraocular diseases such as proliferative vitreoreitnal disorders. The microsurgical tool may be configured to provide the surgeon with improved methods for the removal of proliferative membranes from the surface of the retina or for the removal of residual cortical vitreous proliferative membranes from the areas surrounding the macular hole.
2. Description of the Background
Proliferative vitreoretinal disorders are manifested in the intraocular cavity of the eye by the growth of proliferative membranes on the neurosensory retina. In the conventional treatment for vitreoretinal disorders, the membranes are removed from the neurosensory membranes with various microsurgical instruments such as intraocular forceps and intraocular picks. The microsurgical instruments are introduced into the intraocular cavity through an incision in the eye, and the membranes are carefully removed from the neurosensory surface of the retina without causing tears or hemorrhages.
Depending on the stage of the disorder and the growth of the membranes, the membranes have a different texture and composition. Mature membranes tend to be removed with less complication when compared with the removal of immature membranes. With conventional intraocular forceps and picks, the surgeon is generally able to remove mature membranes from the surface of the retina as a film. When the mature membranes are removed as a film, more complete removal from the surface of the retina is possible with a lower chance of membranes remaining on the surface. On the other hand, immature membranes tend to be friable in nature because they have not acquired the necessary cross-section to be removed with conventional intraocular picks and intraocular forceps. Being friable in texture, the immature membranes do not peel of as a film, and consequently, immature membranes, which are not fully removed during surgery, may be a nidus for future membrane formation, causing the patient to undergo future operations for removal of these membrane formations.
A recent invention, effective in the treatment of proliferative vitreoretinal disorders, has been developed to mechanically remove mature and immature proliferative membranes from the neurosensory surface of the retina without the use of intraocular picks or intraocular forceps. This invention described by Tano, et al. (U.S. Pat. No. 5,921,998 (""998), incorporated herein by reference) uses an abrasive media on a tip of the microsurgical instrument to scrape the membranes from the surface of the retina. The advantages of this invention are a reduced chance of retinal tearing and hemorrhaging and the ability to remove membranes despite the stage of the growth of the membrane.
The abrasive media of the ""998 instrument is affixed on the distal end of a straight probe. The straight probe is introduced into the eye through a cannula that is inserted through an incision into the intraocular cavity in the eye. The abrasive media described in the ""998 patent may be diamond, silicone carbide, quartz, or alumina. The abrasive particles are biologically inert and bonded to the distal end of the probe in a manner such that the shedding of particle into the retinal tissue is avoided. By using different instruments having tips with varying types of abrasive particles, it is possible for the surgeon to more carefully separate and remove these proliferative membranes from the retina without causing damage to the retina. The removal rate may be varied depending upon the type of particles that are bonded to the tip of the microsurgical instrument, where the rate of tissue removal is in proportion to the coarseness of the particles bonded to the tip. The surgeon may more carefully control the removal rate of the proliferative membranes ensuring retinal tears and other damage to the retina does not occur, in distinction to other methods that use intraocular picks and forceps to remove the proliferative membranes.
During surgery for the treatment of vitreoretinal disorders, the surgeon may use in conjunction with these previously mentioned surgical instruments other more common surgical instruments to execute the other functions required during the operation. These microsurgical instruments are also introduced into the intraocular cavity through the cannula. A common instrument is one that is designed to deliver an aspiration source locally to an area to remove tissue. Another common instrument is used to provide infusion to the surgical area for irrigation and flushing as required. The surgeon may use a combination of these instruments and techniques to condition the surface of the retina and remove membranes by the devices previously mentioned. In some conventional instruments, a single instrument capable of performing both of these functions has been used to perform both aspiration and infusion functions.
Other common instruments aid in the visualization of the surgical site. Often the surgeon wishes to illuminate the surgical site or surface of the retina for more complete visualization of the membranes. In conventional instruments, the surgical site may be illuminated or visualized by a fiber optic cable fitted into a probe that is inserted through the cannula into the eye. The fiber optic cable may also be fitted onto a conventional probe to transmit a video picture signal back to a display to give the surgeon a visual image of the surgical site on the surface of the retina. This enhanced visual representation of the surface of the retina allows the surgeon to evaluate the operation and to more completely remove the proliferative membranes during the operation.
Generally, during the course of the operation, the surgeon must alternate between probes to carry out the specific function required at a particular stage of the operation. When changing probes, the old probe must be removed from the cannula and a new probe must be inserted. Generally, the type of cannula used is either straight or curved depending upon the instruments to be used during the surgery and the location of the surgical site in relation to the incision site. Curved probes cannot be inserted through straight cannulas, and straight probes cannot be inserted through curved cannulas. In a surgical procedure using these conventional instruments, the surgeon must make an initial choice to the style or cannula and instrument to be used during the operation.
Sometimes, the surgeon will find that during the course of the operation, a surgical instrument having a straight probe will not efficiently deliver aspiration or infusion to the target area. This may be due to the positioning of the incision or instrument entry site in the eye relative to the target surgical site. The surgeon may decide that a curved probe would provide better range to deliver infusion or aspiration to the surgical site. This change also requires a change in the style of cannula or the use of the probe through the eye incision itself. Such a changeover complicates the operation and often produces additional and sometimes harmful stresses on the eye. Similarly, the delivery of the optical fiber to the surgical site is generally through a straight probe so that the surgeon may directly visualize or illuminate the affected area. Curved probes may also be used with curved cannulas that are aimed to the surgical site. The changeover also complicates the operation and often produces additional and sometimes harmful stresses on the eye.
To overcome these disadvantages of prior art microsurgical instruments used during ophthalmic surgical operations, what is needed is a microsurgical instrument, which combines the functions of infusion and aspiration with abrasive membrane scraping or the functions of illumination with abrasive membrane scraping. The invention could be provided in an adjustable curved member that is adaptable to a straight cannula, thus providing the surgeon with increased range for membrane scraping. The invention could also be provided in a pick and scraping device that could increase the versatility of the instrument introduced to the surgical site. Such an invention would thereby increase the likelihood of success of an operation for removal of vitreoretinal proliferative membrane disorders and other intraocular diseases without undue stress on the tissue surrounding the entry incision.
The microsurgical instrument of the present invention allows the surgeon to treat proliferative vitreoretinal membrane disorders more effectively with less chance of hemorrhaging and tearing. The microsurgical instrument of the present invention combines the advantages of abrasive membrane scraping with the features of aspiration/infusion, and the advantages of abrasive membrane scraping with illumination. In the preferred embodiments of the invention, the microsurgical tool is configured with abrasive particles that are made from synthetic diamond. The diamond particles are preferably contained on a film that is bonded to the distal end portion of the microsurgical instrument. The microsurgical instrument may then be introduced into the intraocular cavity through a straight cannula inserted in through an incision in the eye.
In one embodiment of the apparatus of the invention, the illuminated diamond dusted membrane scraper, the microsurgical instrument has the ability to scrape the membrane surface while providing illumination of the surface to be treated. In this embodiment the apparatus of the invention includes an instrument handle, a tip extending outward and away from the instrument handle, and an adapter fitted onto a distal end of the tip. Preferably, the adapter is cylindrical in shape and has a bevel section-cut across its outside cylindrical surfaces. The abrasive particles are bonded to the outermost tip of the adapter. The instrument handle, tip, and adapter have hollow interiors that are configured to receive and encase an optical fiber. The optical fiber is capable of transmitting/receiving visual imagery or providing illumination. The optical fiber may be positioned through the bevel section-cut in the adapter to illuminate the adapter or transmit/receive visual images of the surgical site. Preferably, the adapter is a flexible and translucent member to facilitate scraping and transillumination.
The second embodiment of the present invention, the illuminated diamond dusted membrane scraper, is similarly constructed. In this embodiment of the invention, the microsurgical instrument includes an instrument handle and a tip extending outward and away from the instrument handle. The instrument handle and tip have a hollow interior; however, in this configuration, the adapter is affixed to a bracket connected to the distal end of the tip, and the adapter is positioned at an acute angle to the tip with the adapter distal end projecting away from the tip distal end. The abrasive particles are deposited on the outermost edge of the adapter. The optical fiber is positioned in the hollow interior of the instrument handle and the tip such that the operative end of the optical fiber is positioned at the distal end of the tip. In this configuration, the optical fiber may illuminate the surgical site or transmit/receive visual imagery of the surgical site. The path of transmission/receipt from the optical fiber intersects the adapter distal end. The surgical site may be illuminated or visualized directly while the surface is scraped by the adapter.
An additional embodiment of the apparatus of the invention has the ability to scrape membranes, while providing infusion or aspiration to the surgical site. In this configuration the microsurgical instrument includes an instrument handle, a tip extending outward and away from the instrument handle, and an adapter fitter on the distal end of the tip. The abrasive particles are contained on the adapter. The instrument handle, tip and adapter have hollow interiors. The hollow interior of the instrument handle may be configured to accept an interface from an external infusion source or an aspiration source. The microsurgical instrument may be introduced into the intraocular cavity, and the adapter may be used to scrape the retinal surfaces. The hollow interiors of the instrument handler, tip and adapter form a channel inside the microsurgical instrument to deliver infusion/aspiration functions to the surgical site.
In another embodiment of the apparatus of the invention, a diamond dusted membrane scraper having a pick with an adjustable stiffness is provided. In this embodiment of the invention, the microsurgical instrument includes an instrument handle, a tip extending outward and away from the instrument handle and an adapter fitted onto the tip. The instrument handle, tip, and adapter have hollow interiors that are configured receive and encase a pick that may be retracted or extended from a hole in the outermost end of the adapter. The pick has a relative stiffness that is indirectly proportional to a length of the pick exposed from the outermost end of the adapter. When the length of the exposed pick is increased, the stiffness of the pick decreases. The stiffness of the pick is adjustable through a control mechanism on the instrument handle that adjusts the length of the pick exposed from the outermost end of the adapter. The amount of stiffness of the pick is controlled by the surgeon to allow the surgeon more flexibility in removing membranes affixed to the surface of the retina. The pick may be fully retracted into the hollow interior of the microsurgical instrument so that the surgeon may utilize the scraping capability provided by abrasive particles deposited on the adapter. The surgeon may also vary the relative stiffness of the adapter by controlling the length of the pick retained in a portion of the hollow interior of the adapter.
In a similar embodiment of the apparatus of the invention, a directional endoscopic abrasive aspiration instrument is provided. In this embodiment of the invention, the microsurgical instrument includes an instrument handle and a tip extending outward and away from the instrument handle. The instrument handle and tip have hollow interiors that are configured to receive and encase a tube that may be retracted or extended from a hole in the distal end of the tip. The extension of the tube is adjustable through a control mechanism on the instrument handle that adjusts the length of tube exposed from the outermost end of the tip. Abrasive particles are deposited on the exterior of the tube at its distal end. Preferably, an elastic nitinol tube is used and pre-formed with a curved distal end. The curvature of the tube may be controlled by controlling the length of tube that is retracted or extended from the tip. In the fully retracted position, the tube is fully contained within the tip and may be inserted into a straight cannula into the incision in the eye. When inside the eye cavity, the tube may be extended from the tip allowing the tube to bend and curve to reach areas that may have been unreachable by a straight instrument. The hollow interior of the instrument handle may be configured to accept an external device to provide aspiration/infusion functions at the distal end of the tube. Simultaneously, the surgeon may remove membranes by scraping the retinal surfaces with the distal end of the tube. The retinal surfaces may be conditioned as required through infusion and tissue may be removed through aspiration.
With the constructions and arrangements of the ophthalmic microsurgical tools mentioned above, it is possible to more effectively remove the vitreoretinal proliferative membranes without excessive damage to the retina and without undue stress to the entry incision into the intraocular cavity.